Pulling nettles leaves gardener smarting

July 22, 2006|B. ROSIE LERNER Purdue University Extension

Q. My husband pulled out a weed in the garden that made his hands burn for a while. It had sharply serrated leaves that were opposite. The stem looks almost square and ropy, with fine hairs along the whole length. Do you have any idea what it is? A. Stinging nettle is most likely the culprit, with its stinging hairs along the stems and on the undersides of the leaves. These perennial plants grow 2 to 7 feet tall and have opposite leaves with saw-tooth edges. The plants have greenish, non-showy flowers. According to the Purdue Veterinary School's Web site on poisonous plants (www.vet.purdue.edu), the small, hollow hairs in stinging nettle contain several irritating substances, such as histamine, serotonin, acetylcholine and formic acid. These substances, coupled with the hairs' ability to scratch the skin and mucus membranes, result in almost immediate burning, itching and irritation. The irritation usually resolves on its own. Q. I have these stickery weeds growing in part of my yard. They are spreading to more of my garden and part of my backyard by the garden. They have a long white root. I've tried pulling them out, but they seem to keep spreading. I'm afraid to spray them in my garden because of the food. Can you tell me what to do to get rid of them? A. Herbicides that would kill broad-leaf weeds also would be likely to damage the vegetables you are trying to grow. There are a few pre-emergence herbicides (such as those that contain trifluralin) that can be applied to garden soil around some (but not all) vegetable crops, but these are aimed at preventing new weeds from germinating from seed. To control existing weeds, hand-pulling and shallow hoeing or tilling around the veggies are your safest methods of weed control. Mulches will help discourage new weed growth. The Purdue Extension office in your county can help you identify the specific weed, if you bring them a sample, and perhaps be able to make more specific control recommendations. Q. I am looking for information regarding a product to prevent the sweet gum trees from producing their gumballs. This spring, I was told that there is now a product, but so far, I have found nothing on the Internet. These gum balls are a big problem for me. I live on one-and-a-half acres and have at least 25 gum trees. A. I'm afraid there really isn't a practical solution for completely preventing fruit on large, well-established trees, but there are some hormone-based products that can help reduce fruit set. One such product is ethephon, sold as Florel Brand Fruit Eliminator. It must be applied at just the right dosage, at just the right stage of flowering (full bloom), and at just the right temperature range. There is risk of plant damage if dosage and/or temperature are too high. In fact, plant stress of any kind can increase the likelihood of plant damage. And, because the product must be sprayed on, the effectiveness will depend on being able to get complete coverage of the canopy, not an easy task on a large mature tree. There is another product called Snipper that is designed to be injected into the tree while the flowers are still in bud stage. However, the application uses a micro-injection system that requires skilled precision. Like other hormone treatments, timing and dosage are critical. This product should be applied only by a professional. You might want to contact a certified arborist for estimates on both of these methods. The price of fruit prevention might make sweet gum fruit cleanup a bit easier to accept! B. Rosie Lerner is a consumer horticulturist for the Purdue University Cooperative Extension Service. She has authored or co-authored nearly 1,000 extension bulletins, articles, book chapters and books, and is a former state coordinator of Indiana's Master Gardener Program. Visit the extension Web site at www.ces.purdue.edu.